Recovery of Waste Polystyrene Generated by Lost Foam Technology in the Automotive Industry

In the automotive industry, lost foam casting is a relatively new technology, which is gaining popularity among manufacturers. Lost foam casting is a process in which an expanded polystyrene pattern is formed into the shape of the part to be cast. More complex parts are fabricated by simply gluing several simple patterns together. The pattern is then coated with a refractory material consisting of a mineral mixture and binders. Finally, hot metal is poured into the pattern, evaporating the expanded polystyrene and taking shape of the coating shell. However, the automotive industry has observed that a significant number of these fabricated, coated patterns are damaged, or do not meet specifications prior to casting. These are not reusable and inevitably are landfilled. It is the goal of this project to develop a simple, reliable, and inexpensive technology to recover expanded polystyrene from the glue and coating constituents. This study includes an investigation of the size distributions of each component (polystyrene, coating, and glue) upon shredding, air separation/classification, and the effectiveness of impact milling. Separation testing has recovered as high as 96% of the polystyrene, while the level of contaminants did not exceed 5 wt% in the final product. These results indicate that a promising technological approach has been selected and that realization of a separation technology is feasible.